Contact connection for printed circuit products



March 5, 1963 H. SHORTT CONTACT CONNECTION FOR PRINTED cmcurr PRODUCTS Original Filed Oct. 20, 1954 an man No E U H/% Y B ATTORNEY 3,079,674 CONTACT CONNECTION FOR PRINTED CIRCUIT PRODUCTS Hubert L. Shortt, Tarrytown, N.Y., assignor to Technograph Printed Electronics Inc., Tarrytown, N.Y. Original application Oct. 20, 1954, Ser. No. 463,475.

Divided and this application No 26, 1958, Ser. No.

7 Claims. (Cl. 29-1555) The present invention relates to printed circuit prodnets, and more particularly to' contacticounections for printed circuit products and to a method of making such contact connections: g

Printed circuit products-generally comprise"; a conductive pattern representingia circuit-system or a circuit component supported on an insulation backing adhering "ice In the drawing:

H6. 1 is a fragmentary sectional view ofa printed circuit product with which a conductor is to be connected.

FIG. 2 is a sectional view similar to 'FIG. 1 showing the first step of preparing a junction point between the circuit product and a conductor.

FIGS. 3, 4 and 5 show successive stages of making the contact connection.

FIG. 6 is a sectional view of the completed contact connection, and

FIG. 7 is an enlarged sectional view of the completed contact connection to illustrate the homogenity of the contact connection.

Referring now to the figures in detail, the figures show a metallic conductor 1 which may be visualized as one of the-pathways ofa conductive pattern produced by any printed circuit technique. Conductor 1 is secured to an insulationbase Z by any means suitable and known for-the purpose, for instance, by an adhesive layer 3. In this connection itshould be mentioned that at least the thickness of the conductor 1 is greatly exaggerated. In

- actual practice, this conductor is usually in the order of tice, it may vary between paper thin insulation sheets and solid blocks of insulation material.

Irrespectively of the thickness of the insulation backing, the problem often arises to make high quality contact connections with the conductive pattern through the insulation backing. The quality of the contact connections foil thickness.

Let it now be assumed that a contact connection according to the invention is to be made between a wire and conductor 1 through insulation backing 2 and adhesive layer 3. To prepare the junction point of the conductor for this purpose, a hole 4 is drilled or otherwise made through the entire structure. FIG. 2 shows this step of the operation. The diameter of this hole should be slightly larger than the diameter of the wire to be connect- 3 ed to conductor 1.

A wire 5 to be connected is now inserted through the hole, with the end of the wire slightly protruding from the upper plane of conductor 1. The protruding end of the wire is slightly enlarged or headed by a tip or cap 6 v of soft solder or an equivalent conductive matereial as is shown in FIG. 3. Tip 6 may be applied to wire 5 either and improved contact connection which combines high quality contact characteristics with high quality mechanical properties;

Still another object of the invention is to provide a novel and improved contact connection in which the contact material constituting the conductive pattern and the material constituting the contact connection proper form a substantially 'tionsgeneeusbed thereby assurin'g'an electrically practically perfect connection and a strong mechanical bond between the conductive pattern and the contact connection.

A further object of the invention is to provide a novel and improved contact connection which is substantially flush with the outer surface of the conductive pattern proper. This affords the advantage that the printed circuit product may suitably coact with a sliding contact as is required for instance, in the telephone art in connection with selector switches or relays, or may constitute a component of a capacitative coupling.

A still further object of the invention is to provide a novel method of producing the afore referred to contact connections which method permits to produce the contact connections in an inexpensive, simple and uniform manner.

Other and further objects, features and advantages will be pointed out hereinafter and set forth in the appended claims forming part of the application.

In the accompanying drawing a preferred embodiment of the invention is shown by way of illustration and not by way of limitation in conjunction with which the method according to the invention will be further explained.

before or after insertion of the Wire in the hole. This figure also shows that there is a narrow annular clearance 7 between conductor 1 and wire 5.

The next step is to retract wire 5 back into the conductor hole so that the soft solder material is forced into space 7 and fills the said space as completely as practical. FIG. 4 shows wire 5 retracted into a position in which. its end is substantially flush with the outer surface of conductor 1, the surplus solder material 6 forming a protruding blob.

Thereupon the surplus 'so'lder material is' removed by a suitable machining operation such as planing or shaving to level the surface of conductor 1 and wire 5.

As is apparent from the previous description, wire 5 is now connected with conductor 1 by the strong electrical and mechanical bond formed by solder material wedged into annular space 7. The bond between wire 5 and conductor 1 may be further strengthened, if desirable, by applying sufiicient heat to melt the soft solder to form a hot solder joint.

The contact connection can be further improved by coating the entire conductor l or at least the vicinity of the junction point with a metal layer '8. This layer may be made of the same metal as used for conductor 1 but may also be of a metal selected to produce any desired property of the surface of conductor 1 which is either lacking or insufiicient in the metal of which the conductor is made. For instance, the metal of the layer may be such as to improve the electrical or thermal conductivity of the conductive pattern, or the wear and abrasion resistance, or the corrosion and are resistance thereof. Layer 8 may be produced by any means suitable for the purpose such as electro-deposition.

' The result of the aforedescribed operations is an ex cellent electrical and mechanical connection between condoctor 1 and Wire 5. Conductor 1, wire 5, layer 5 and the solder material 6 forced into annular space '7 constitute a homogeneous body for all practical purposes. This is symbolized in FIG. 7 byshowing layer 3 as part of the conductor proper. Thisfigure also shows the intimate connection between conductor -1 and Wire 5 established by the solder material 6 in space 7. tact surface of conductor i, or more 5 ccifically of layer 8 is perfectly smooth and unbroken, the connection proper being 'mvisible' As a result, a conductive pattern connccted by a connection according to the invention lends itself to coaction with devices employing wiper contacts, or to use as a component'of a capacitative coupling. In either case, the distance between the surface of the con ductive'pattcrn'and the respective surface of the coasting therewith must'usually be 'in'the order of-a few thousandths of an inch which necessitates smoothcontact surfaces.

While the invention has been described indetail with respect to a wrtain now preferred example and-embodiment of the invention it will be understood by those'sicilled in the art after understanding the invention, that'vaiious changes and modifications may be made Without departing from the spirit and scope of the invcntion and it is intended, therefore, to cover all such changes and modifications in the appended claims.

This application is a division of my copendiug application Serial No. 463,475, filed October 20, 1954, and

now' abandoned.

What is claimed as new and desired to be securedby Letters Patent, is: t

1.A method of connectinga wire conductor to an'insulation-backcd conductive foilpattcrn of a printed circuit,

said method comprising the steps of providing through the conductive pattern of the printed circuit product a hole having a diameter larger than the diameter of the conductor to be connected, securing to one end of the wire conductor an enlarged tip of soft conductive material,

inserting the Wire conductor in said hole with the tipped part,

- cess sort conductive material and .theconductor part from The produced concircuit pro-duct of "a hole having diameter slightly larger than the diameter of the conductor to be con nested, fitting the conductonin said hole from the insula-.

tion side of the'printed circuit product and sli htly protruding from the pattern side thereof, applying a tip of a soft conductive 'materialhaving "a peripheral outline slightly larger-than said hole to the protruding portion of the co'uductonisaid tipbeing applied spaced'apart from the conductive pattern, retracting the conductor into a position in which part of the soft material is deformed by cold flow and wedged into the clearance between the conductor, and the'conductive pattern thereby filling the said clearance, and removing protruding soft surplus material from the outer surface-of the conductive mate rial thereby leveling the said surface.

'5. The method according to'claim 4, wherein said soft material is soft solder and comprising the additional step of heating the soft-solder to form a hot solder joint.

-6."lhe mcthod'according to claim 4 and further comprising the step of coating the surface area surrounding said hole,-.the'conductor fitted in said hole and the soft material filling said clearance with a layer of metal.

17. A method according toclaim 6, wherein the said coating step is effected by electro-deposition of metal.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A METHOD OF CONNECTING A WIRE CONDUCTOR TO AN INSULATION-BACKED CONDUCTIVE FOIL PATTERN OF A PRINTED CIRCUIT, SAID METHOD COMPRISING THE STEPS OF PROVIDING THROUGH THE CONDUCTIVE PATTERN OF THE PRINTED CIRCUIT PRODUCT A HOLE HAVING A DIAMETER LARGER THAN THE DIAMETER OF THE CONDUCTOR TO BE CONNECTED, SECURING TO ONE END OF THE WIRE CONDUCTOR AN ENLARGED TIP OF SOFT CONDUCTIVE MATERIAL, INSERTING THE WIRE CONDUCTOR IN SAID HOLE WITH THE TIPPED END OF THE CONDUCTOR PROTRUDING FROM THE OUTER SURFACE OF THE CONDUCTIVE PATTERN AND THE REMAINDER OF THE CONDUCTOR PROTRUDING FROM THE INSULATION BACKING, SAID TIP 